A typical commercial bakery oven has a housing within which are mounted a plurality of burner tubes that extend from one side of the housing to the opposite side. Such an oven conventionally has one or more movable product conveyors which convey goods that are to be baked along a path from one end of the oven to the other. At intervals along the length of the oven are burners which extend transversely of the path of movement of the goods to be baked. Conventionally, each burner comprises a hollow tube having an outlet slot along one side thereof through which flows a combustible fuel, such as gas. At one end of each tube is a source of fuel and an igniter by means of which the fuel is ignited as it flows outwardly through the slot of the burner tube wall.
Each burner tube conventionally extends from one side of the oven toward the opposite side and has a length of ten to twelve feet, or more. It is conventional to ignite the fuel at that end of the burner tube which is adjacent one wall of the oven so that, during start up operation, a continuous flame is generated in a direction from the igniter to the opposite end of the tube which terminates adjacent that wall of the oven which is remote from the wall through which the burner tube extends. A finite period of time is required for the flame to be propagated from the igniter end of the tube to the remote end thereof at which the presence of a flame may be sensed by a conventional flame sensor. When the flame is sensed, operation of the igniter terminates. In some instances, however, and for one reason or another a flame does not extend all the way from the igniter end of the burner tube to the remote end. This is undesirable because unburned fuel is discharged to the interior of the oven and the heating of the oven is not as efficient or as effective as it should be. Accordingly, it is desirable to be able to sense the presence of a flame at such remote end of each burner tube.
A principal object of the invention is to provide apparatus for sensing the presence of the flame at the remote end of the burner.